Parental beliefs about vaccination are one of the main factors in reaching high vaccination rates. This cross-sectional study aims to assess the awareness and attitudes regarding routine childhood immunization among Saudi parents in Riyadh, Saudi Arabia. This survey, with a pretested 18-item questionnaire, was conducted on parents having at least one child from Riyadh, Saudi Arabia, between 1 May 2019 and 1 November 2019. The validated questionnaire consisted of three sections; participants’ demographics, awareness, and attitude regarding the immunization of their children. In total, 1200 parents participated in the study, 883 (73.3%) of the parents scored a good knowledge of childhood immunization, and 93% knew that routine vaccination protects children from infectious diseases and their complications. Around 10% stated that immunization can cause autism. Only parents in age groups 30–39 and 40–49 were 1.76 (p < 0.05) times and 1.92 (p < 0.05) times, respectively, more likely to exhibit good knowledge. About 522 (43.6) of the parents attained a positive attitude toward immunization. Adherence to the immunization schedule was confirmed important by 93%, while 91% presumed that immunization keeps their children healthy. Additionally, immunization was perceived as important by 94% of parents and only 8% agreed that immunization is prohibited by religion. Females were 1.45 (p < 0.05) times more likely to exhibit positive attitudes than males. Parents have good knowledge and a positive attitude towards child immunization. However, parental education should be focused on the fact that religion supports immunization, and more awareness should be focused on the lack of correlation between autism and vaccination.